Heart disease: have we got it all wrong?

Heart disease: have we got it all wrong?

THE HEART is a lonely muscle. It sits behind the rib cage, pumping 100,000 times a day to carry nourishment to the farthest extremities of the body. Eulogised, mocked and celebrated by lovers, it is a vulnerable organ, prey to the excesses of a Western lifestyle. But there is good news. The heart is getting stronger.

Heart disease deaths in Britain are plummeting - by 3,000 in 2000 alone. Between 1988 and 1998, they have fallen 39 per cent. Over the past three decades, they have halved. Fewer people today die of a failing heart before the age of 75 than at any time in the past half-century.

In 1995, cancer overtook heart disease as the chief cause of death among men in Britain. That was not because cancer deaths were rising, but because of the spectacular fall in deaths attributable to the ailing heart.

The reasons for the decline remain puzzling. No single factor can account for the size and speed of the fall in deaths. Improved treatment, more surgery and wider prescription of drugs have helped. So have certain changes in lifestyle, such as the fall in smoking.

But obesity is growing, we take less exercise than we did and the amount of fat in our diets is largely unchanged. No one fully understands what is happening.

The uncertainty stems from our ignorance of what caused the heart disease epidemic. It began in the Forties, rose to a peak in about 1970 and then began to fall. All Western countries were affected and all followed broadly the same pattern.

But despite decades of research and the expenditure of billions of pounds on research, the causes of the epidemic remain a mystery.

Coronary disease is so called because it affects the 'crown' or corona of arteries that sit on top of the heart and provide oxygenated blood to the heart muscle to keep it pumping.

These small arteries are prone to the narrowing caused by atheroma, the thickening of the artery wall caused by fatty deposits containing cholesterol.

When a clot of blood or 'thrombus' comes along, it may become lodged in the narrowed artery, blocking the supply of blood to the heart muscle and causing a coronary thrombosis or heart attack.

At first, attention focused on the causes of atheroma and the role of cholesterol in the narrowing of the arteries.

LARGELY thanks to the work of the American epidemiologist Ancel Keys, heart disease came to be seen as a nutritional disorder linked with the quantity of fat in the diet.

If this could be reduced, Keys argued, cholesterol levels would fall and the arteries would be protected from atheroma.

The nutritional theory has held sway for 50 years and the central role of cholesterol is accepted by the World Health Organisation.

'People with high cholesterol have a higher risk of heart disease and the evidence for that is clear from around the world,' said Pekka Puska, director of non-communicable disease prevention at the WHO.

But persuading people to change their diets has proved tougher than doctors expected.

Total fat consumption in the UK has hovered around 40per cent of total calories for the past 25 years, although saturated fat - the 'bad' sort - has come down from 20 per cent to 15 per cent.

There has also been a modest increase in fruit and vegetable consumption, from 1,800 grams a week to 2,200 grams, and a fall in salt consumption.

Similar changes have been seen in many Western countries in recent decades and blood cholesterol and blood pressure levels have fallen, albeit modestly.

Smoking, which increases the stickiness of the blood and its propensity to form clots, has also come down.

The change in these three key risk factors accounted for two-thirds of the fall in heart disease deaths, according to the WHO's Monica ( monitoring cardiovascular disease) study, which compared rates across Europe.

The remaining third was due to better survival - people were living with heart disease rather than dying of it, due partly to better treatment.

But the study failed to show the expected correlation with fat consumption in different countries - and added to confusion about the causes of heart disease.

Other puzzles remain. Heart disease is an epidemic that has largely affected men. If it had not occurred, there would have been 1.2 million fewer premature deaths among men over the past 50 years. Yet from the Forties onwards, smoking, fat consumption and blood pressure - the main risk factors for heart disease - increased equally in women.

Indeed, a Bristol University study published in the British Medical Journal in 2001 showed that women who consumed the most fat had the lowest rate of heart disease.

The conventional explanation is that women are protected by the female hormone oestrogen.

BUT if that were the case, the increase in male heart disease should have been paralleled by a similar increase - but to a lower level - in women. The fact that this did not happen casts doubt on the hormonal theory.

Professor Shah Ebrahim, an author of the Bristol study, says there is likely to be some biological difference in the way women respond to dietary fats. But it remains unexplained.

A further puzzle is the socalled 'French paradox'. Their passion for meats and cheeses pushes their fat consumption to 41 per cent of total calories, the highest in Europe.

Yet French rates of heart disease deaths in the under-75s are less than half those in Britain. Professor Sir Charles George, medical director of the British Heart Foundation, believes this can be explained.

Records show that although heart disease deaths are lower in France than in Britain, other cardio-vascular disease deaths are higher. Unclassified deaths are also higher in France.

Thus it is not the regular verre du vin rouge which is conventionally thought to protect the French heart, but the French bureaucrat.

While the decline in heart deaths is remarkable, it is too soon for celebration.

The disease still causes 70,000 premature deaths (in people aged under 75) a year, and Britain remains near the top of the world league.

The best way to avoid heart disease is to choose your parents carefully - genes play the greatest part - and ensure your mother eats well before conception and during pregnancy.

Small babies are more likely to develop heart disease in adult life and the increase in birth weights over the past century may have contributed to the fall in heart deaths.

Eating less fat, more fruit and vegetables and taking exercise provide some defence.

But there is cause for alarm. There are signs that the 30-year fall in heart deaths may be coming to an end.